In portable information terminals, software switching is used more often than hardware switching. When using software switching, a system is driven by pressing an device (e.g. a pen) onto a predetermined area of a touch screen panel ("TSP") which covers a liquid crystal screen and a program selection screen. When the system is to be turned off, a "turn-off" command is applied by pressing the pen on a certain area of the touch screen panel.
A conventional portable information terminal using software switching may contain one of two different activation areas on which a pen may be pressed to activate the terminal. The first activation area may be an icon image occupying a small area in the program selection area of the touch screen panel. The second activation area may correspond to the entire touch screen panel.
With respect to the first activation area, attention must be paid to ensure accurate selection since the activation area is small. With respect to the second activation area, a touch screen panel protection cover can inadvertently touch the touch screen panel when the portable information terminal is being transported in a briefcase, bag, etc. Thus, a microcontroller in the terminal may mistakenly assume that the pen is continuously pressed on the touch screen panel and the terminal may be erroneously turned on. As a result, power is consumed unnecessarily.